GM (NYSE: GM) is showing rising problems in its light truck operations. Pick-up and SUV sales seem to be getting hurt by housing problems and relatively high fuel costs.

After shutting shifts at several U.S. plants, the action is moving to Canada. According to Reuters, the car company will shut down a shift in Oshawa, Ontario, and lay off 1,000 workers.

GM and Ford (NYSE: F) are facing a much harsher environment than they were when they began cutting billions of dollars in costs. The hope then was that if they could hold market share in the U.S., their North American operations would become profitable. The current negotiations with the UAW are part of a strategy to pick up the pace of that process.

What GM probably did not expect was a near-recession in the part of the market which tends to buy pick-ups. Builders and blue collar workers are in the midst of an economy that is pinching their incomes.

GM has done a lot right, but what it cannot control may be its worst enemy.

Douglas A. McIntyre is a partner at 24/7 Wall St.